The invention relates to a data transmission method, which is used in a radio system comprising at least one base station and terminal equipment comprising a receiver and a transmitter and communicating with each other over at least one physical channel.
The invention further relates to a radio system, particularly a radio system comprising at least one base station and terminal equipment comprising a receiver and a transmitter and communicating with each other over at least one physical channel.
Present mobile telephone systems attempt to provide the user with increasingly versatile services. This goal is shared by IMT-2000 (International Mobile Telecommunications for the Year 2000) services which aim to offer high-quality speech/audio signal transmission, high-rate data transfer, photograph transmission and video image transmission. In addition, the IMT-2000 service encompasses interactivity, multimedia electric mail, video conferences and target location determination, for example.
Transferring different data requires different symbol rate and signal transmission power. In the present radio systems the symbol rate is not optimized for the changing channel conditions since the symbol rate of several signals cannot be adapted in one physical channel. If, for example, two service signals transmitted over the same physical channel have differing quality requirements when received and the signals act differently when the delay profile of the channel changes, problems affecting the power level of the two signals occur. Such a problem typically arises when Reed-Solomon coding and convolution coding are used together. When the channel delay profile changes, a situation may arise when the first signal in accordance with the example is barely acceptable in terms of quality, while the other signal is of unnecessarily high quality. The simulation is particularly critical when a service signal only requiring a low symbol rate forces a service signal requiring a high symbol rate to use extra transmission power. The prior art solutions fail to resolve this disparity. Unresolved, the disparity will cause interference over the whole area of the radio system.
An object of the invention is thus to provide a method and a radio system implementing the method so as to solve the above problems and balance the signal quality. This is achieved by a method of the type described in the introduction, the method being characterized by the transmitter transmitting at least over one physical channel at least two signals having differing quality requirements when received, and the transmitter changing, if necessary, signal-specifically the symbol rates of the signals used over the physical channel in order to meet the quality requirements.
The radio system of the invention is characterized by the transmitter being arranged a transmit over one physical channel at least two signals having differing quality requirements when received, the transmitter therefore comprising at least means for changing the symbol rate of the signals signal-specifically in order to meet the quality requirements, and combination means for combining the signals in the same physical channel.
A plurality of advantage can be achieved with the method and system of the invention. The desired quality requirements of a signal to be received can be balanced, which enables optimized transmission power be used. The result is less interference in the radio system.